1. Field of the Invention
The present invention relates to a method for estimating repair accuracy of a mask shop, which provides a basis for engineers to determine a qualified mask shop.
2. Description of the Prior Art
Masks are frequently used in a semiconductor manufacturing process. A typical mask comprises a transparent substrate such as a quartz substrate and a light-shielding or absorbing layer such as a chrome layer with a thickness of 1000 xc3x85 on the substrate. A phase-shift mask further comprises a layer generating a phase shift for the light penetrating therethrough.
A typical mask manufacturing process comprises the steps of depositing a chrome layer on a quartz substrate, depositing a photoresist layer on the chrome layer, patterning the chrome layer by etching under the masking of the photoresist layer processed by e-beam writing and developing.
Defects on the chrome layer are usually generated after the previously described steps. They include clear defects which are missing parts of the chrome layer and opaque defects which are redundant parts of the chrome layer. A further step of chrome depositing is needed to repair the clear defects. As for repairing the opaque defects, a step of chrome sputtering using FIB (Focus Ion Beam) is implemented.
The repair accuracy of the mask shop is very important due to the shrinkage of ICs and since defects of the chrome layer always exist. Engineers are eagerly to have a estimation basis of the repair accuracy to determine a qualified mask shop.
Therefore, the object of the present invention is to provide an estimating method for the repair accuracy for the engineers to determine a qualified mask shop.
The present invention provides a method for estimating a repair accuracy of a mask shop. The method has the steps of providing a mask having a light-shielding layer with a pattern of a plurality of lines, each of which has a defect, using the mask shop to repair the defects, measuring first widths of the lines where the defects are repaired and second and third widths of the lines aside where the defects are repaired, and calculating ratios of means of the second and third widths to the first widths for estimating the repair accuracy.
Therefore, by using the mask shop to repair the defects on the vertical and horizontal line with different widths, and statistically calculating the errors of the results, the repair accuracy of the mask shop is determined.